CALCIUM CARBONATES EFFECT ON PARTICLE SIZE DISTRIBUTION AND TEXTURE CLASSES IN CALCAREOUS SOILS IN SULAIMANI GOVERNORATE.

This experiment was carried out to study the effect of removal of CaCO3 on particle size distribution (PSD) and texture classes in some soils in Sulaimani Governorate, Kurdistan region, Iraq. Thirty four soil samples were collected from different calcareous soil horizons. These soils were analyzed for CaCO3 and the carbonates were ranged from 51.9 and 42.63 g kg-1. The three weighted soil textures (sand, silt and clay) were determined before any removal of the CaCO3 and after the removal of CaCO3. The sand fraction ranged from 87.6 to 316.0 g gk-1 while the clay fraction ranged from 237.7 to 614.7 g kg-1 and the silt fraction was slightly higher than clay fraction. The results showed that removal of CaCO3 led to a change in PSD in all the samples and 85% of those changed textural class. The carbonates did not show a uniform distribution in soil particle size and generally carbonates were most accumulated in sand and silt size. The soil had the most prevalent PSA change in the silt and sand fractions following CaCO3 removal. The maximum significant correlation between particle size distribution before and after carbonates removal was related to clay particles (P< 0.01) but the correlation was not significant between the silt components. Therefore, we recommend that all calcareous soil samples from the semiarid be pretreated for CaCO3 removal prior to particle-size analysis and subsequent textural classification.